1. Field of the Invention
The present invention generally relates to a paper web guide device equipped with a plurality of guide rollers for guiding a paper web which is conveyed through a processing machine such as a rotary press. More particularly, the present invention relates to a paper web guide device with an automatically controlled self-cleaning mechanism for cleaning the circumferential surface of the guide roller.
2. Prior Art
Various paper web guide device with such type of self-cleaning mechanism have been conventionally shown in Japanese Patent Application Laid-Open Publications No. 62-132644 entitled "Cleaning Method in Rotary Press and Device of the Same"; No. 62-149449 entitled "Cleaning Method for Guide Roller in Rotary Press and Device of the Same"; No. 62-255150 entitled "Cleaning Device for Guide Roller in Rotary Press"; No. 62-256657 entitled "Cleaning Method for Guide Roller in Rotary Press"; Japanese Patent Under Utility Model Application Laid-Open Publications No. 63-33941 entitled "Stain Preventing Device for Guide Roller in Rotary Press"; Japanese Patent Application Laid-Open Publications No. 63-268648 entitled "Cleaning Method for Guide Roller in Rotary Press"; No. 63-268649 entitled "Cleaning Method for Guide Roller in Rotary Press"; No. 64-31641 entitled "Cleaning Method for Rotary Press"; No. 1-204740 entitled "Automatic Cleaning Device for Web Guide Roller" and No. 1-209139 entitled "Guide Roller Device in Rotary Press".
The above described publications wholly relate to the methods and devices to clean the circumferential surface of the guide roller by rubbing the guide surface with the paper web. In these methods and devices, the rubbing motion is generated by controlling the circumferential speed of the guide rollers to be different from that of the travelling speed of the paper web.
For example, the device shown in Japanese Patent Application Laid-Open Publication No. 1-209139 teaches a linkage mechanism which controls the revolving speed of at least one of a plurality of guide rollers to be different from the other guide rollers for driving the guide rollers by the contact-friction force between travelling paper web and the guide rollers. The contact-friction force of the guide roller depends on the wind angle of the travelling web, and therefore the driving force for the guide roller is transmitted to the other guide roller through the linkage mechanism. Thus, the guide rollers are respectively driven at various circumferential speeds which are different from the travelling speed of the paper web.
In the other conventional devices and methods the respective guide rollers are positively controlled by driving means or braking means to forcibly control the circumferential speed of the guide rollers to be different from the travelling speed of the paper web. The conventional devices and methods use either driving means or braking means for positively controlling plural guide rollers.
The above described conventional devices and methods exhibit some problems requiring resolution.
For example, the device shown in Japanese Patent Application Laid-Open Publication No. 1-209139 entitled "Guide Roller Device in Rotary Press" uses the contact-friction force between the paper web and the circumferential surface of the guide roller as the driving force for the guide rollers. According to this device the difference between the travelling speed of the paper web and the revolving speed of the guide roller is autonomously generated within the allowable range of the tension applied to the paper web so as to prevent the paper web from excessive tension. The revolving forces for the respective guide rollers connected through the linkage depend on the wind angle of the travelling web around the respective guide rollers. However, when the difference between the minimum value and the maximum value of the wind angles is excessive, the revolving force depending on the maximum angle is almost not affected by that of the minimum angle. Thus, the revolving speed of the maximum wind angle roller is almost the same as the travelling speed of the paper web. The circumferential surface of this maximum wind angle roller is not effectively cleaned. Consequently, this device will cause a further problem in the design stage in that the selection of the kind, combination, and configuration of the plural guide rollers to be connected with the linkage means are very difficult to determine.
The above described conventional devices and methods, except for Japanese Patent Application Laid-Open Publications No. 1-209139, employ forcible control systems for making the revolving speed of the guide roller to be different from the travelling speed of the paper web by either driving or braking all of the plural guide rollers at the same time. Although this system can effectively clean the respective circumferential surfaces of the guide rollers, the paper web will sometimes be subjected to great tension at the beginning of the driving and braking operations. Particularly, when the travelling length of the paper web is relatively long and many guide rollers are arranged along the travelling path, the tension will be continuously and accumulatively applied to the paper web in its longitudinal direction. As a result, the tension will exceed the allowable value when all of the guide rollers are simultaneously driven or stopped.
In order to resolve this problem, for example Japanese Patent Under Utility Model Application Laid-Open Publications No. 63-33941 entitled "Stain Preventing Device for Guide Roller in Rotary Press" shows a gradual control system for gradually braking or driving the guide rollers in a predetermined order. Alternatively, Japanese Patent Application Laid-Open Publications No. 63-268649 entitled "Cleaning Method for Guide Roller in Rotary Press" shows a method that all of the guide rollers should be driven or braked at the same occasion with decreasing or cancelling the backtension applied to the paper web as requirement and confirming the travelling condition of the paper web at a slow speed. Accordingly, these conventional devices and methods require an extremely long time for cleaning the circumferential surface of the guide rollers by the travelling paper web.